Electricity is simply the flow of electrons through a conductor. Electrons are the tiny negatively charged particles that are found in all atoms. Electricity is transmitted as loose electrons move from one atom to the next within a conductor. A conductor is any material that facilitates this transmittal of electricity.
Most practical applications of electricity require electrons to flow through a circuit. A circuit includes a source of electrons (a battery or generator), an energy-consuming device (such as a light bulb), and conductors (wire) that transmit the electrons to and from the bulb. In the simple circuit shown below, the battery causes electrons to flow through the wire to the light bulb where light is created. The electrons then return to the battery via the wire and the electric circuit is complete. Note that the bulb does not “consume” the electrons, but rather the electrons flow through a material in the bulb causing it to glow.
To begin the flow of electrons through a conductor, a source of energy is required. This can be either chemical or electromagnetic energy. Batteries and fuel cells operate by using chemical energy to free electrons from one material and transfer them to another via a conductor. Batteries and fuel cells contain three components — two electrodes and an electrolyte. The electrolyte reacts with the electrodes to create oxides that result in excess negative charge in one electrode (creating the negative terminal) and excess positive charge on the other (creating the positive terminal). The imbalance in charge creates an electric current when the terminals are connected to form a circuit.
Electromagnetic energy is used in two primary ways to create electricity. Solar or photovoltaic (PV) cells are made of materials that cause electrons to flow when light strikes the cell. As with a battery, the flow is directed through a circuit. The most common way of creating electricity — the electric generator — uses electromagnetic energy in a very different way. An electric generator creates electricity by what is called electromagnetic induction. Electromagnetic induction uses magnetism to make electrons flow. A source of mechanical energy (a steam turbine, gas turbine, wind turbine, or water turbine) is used to spin a shaft connected to a coil. This coil is suspended between the poles of a magnet and is connected to wires in a circuit by metallic brushes. As the coil spins through the magnetic field, electrons flow through the coil and brushes and then into the electric circuit.